This invention is directed towards a class of surface water vessels that include aluminum hulled vessels of about 40 feet that displace over 20,000 pounds of water. These vessels may be unmanned surface vessels (USVs) may be powered by diesel engines and twin propellers or waterjets. The fuel capacity is generally 400 to 800 gallons which translates to a limited endurance while performing the mission for which they were designed. All must be brought to the mission area by a larger host vessel.
Generally, each USV must be retrieved from the sea and brought on board the host vessel to be refueled. This reduces the percentage of time the USVs are conducting their mission, reducing their effectiveness and also causes the host vessel to remain relatively close to the mission area. While recovering, the host vessel may be restricted in course and speed, unable to launch and recover other USVs, and not able to operate other systems, which limits its efficiency. If the host vessel can only launch/recover one USV at a time (as is typically the case), this creates a queuing problem for groups of USVs and subtracts from the total mission time available as all must wait while each unit is replenished and re-launched before returning to the mission area. Deteriorating sea conditions may make recovery difficult, dangerous, or impossible and disrupt the USVs mission.
Recently, the U.S. Navy has been developing and working on arrangements for the at-sea refueling of USVs. There are many difficulties associated with open-water refueling, such as for example, unpredictable sea states, and difficulty in obtaining a proper connection between the USV and the fueling station to avoid spillage. It is therefore desired to have an at sea refueling station that overcomes the pitfalls of at-sea refueling, and obviates the need for using a host vessel to provide this service, allowing the host vessel to conduct other missions simultaneously or stand off from a potentially hazardous area.